The invention relates to a centrifugal disk for impact mills, air classifiers or the like, in particular for seeds having shells, such as sunflower seeds, oats, psilium seeds and the like, having radial channels whose side walls are profiled.
Such centrifugal disks receive the material to be processed, generally via a feed means (pipe, hopper or the like), entering axially and are intended to centrifuge the material radially, it being possible for an impact ring to be arranged around the centrifugal disk. Frequently, such centrifugal disks have a smooth surface so that uniform transport of the grains is then not absolutely ensured. It has therefore also been proposed to provide the surface with furrows or channels through which the grains are carried.
However, it has been found that this measure too is not sufficient under all circumstances, since the granular material can also move in the axial direction and thus either escape from the effect of such a channel open at the top or acquire a different trajectory which deviates from the desired optimum trajectory.
U.S. Pat. No. 4,393,762 has also proposed trapping the grains with the aid of guide plates and introducing them into a channel bordered by parallel walls (i.e. at the bottom by the wall formed by the centrifugal disk itself and at the top by a parallel wall) and into a notch which is triangular in cross-section and which keeps the grain in a predetermined path, similarly to the missile of a catapult of antiquity. Such a means has proven very suitable in principle for certain granular materials to be treated, but there is a striking deterioration in the results in the case of other materials, even in comparison with conventional centrifugal disks of the above-mentioned type. The reason for this remained unclear for a long time and has also meant that this design has not become established in practice.